A known issue associated with opening a DC current is that an arc builds between the contacts of the switch when the contacts are separated from each other. The arc is erosive and may thus damage nearby parts of the switch.
There have been attempts to use a magnetic field, produced by permanent magnets or a coil placed in proximity of the contacts, to blow the arc away to quenching plates. Often the case is that currents close to the nominal current are easier to switch than currents that are small compared to the nominal current. This is because an arc associated with a nominal current seeks to the quenching plates but an arc with low current more easily remains to burn between the contacts of the switch.
However, known techniques for quenching an arc in the switches are either complicated or do not fully meet the demand for durability of the switch.